E30 the biowaste - M20B28 itb race car

[hasa]

Nothing to report here

[hasa]

DIY tool for some valve spring research

[hasa]

I bought dBilas 312 cam in order to get more power above 5000rpm. For some reason it has 1mm bigger base circle than Schrick 304. Lobes seem to run very close rocker slider edges. I hope this combination works.

[digger]

I bought dBilas 312 cam in order to get more power above 5000rpm. For some reason it has 1mm bigger base circle than Schrick 304. Lobes seem to run very close rocker slider edges. I hope this combination works.

Do you mean the toe edge of the rocker pads digs in? install checking spring, paint rocker surface with light coat of grease or prussian blue/dychem and spin it over by hand to make sure the contact patch is not all the way to the toe end of the rocker. If it goes to the edge it will not last and needs to be rectified

[hasa]

It is not "all the way" to toe edge, but closer than with Schrick 304. I think this may be hottest non-roller cam I'll ever try with M20.

[digger]

close is perfectly fine

[temashka-b27]

does anyone have any experience with this?

[digger]

does anyone have any experience with this?

with what?

[Jb325is]

Great thread. Lots of good parts on this car and its good to see some serious track/race cars on here.

How are you liking the BC's and what rates did you go with on the coilover rear? Looks like you are running the car pretty level, as in minimal rake? Or is that just the rear fenders that make it look that way.

What diff are you running?

[hasa]

Thanks! I like those BC's but mine are customized by one local suspension specialist. He said that BC is good starting point as race coilovers, but he changes oil and shimming before giving them to customers. I don't know the damper rates, but springs are 120kg/cm front and 50kg/rear = very typical setup for a 300-series BMW with semi-slicks.

Regarding rake, I believe that pictures just lie?

Diff is 188 4.10 with Quaife.

[hasa]

Thanks to digger I started to doubt my observations about rocker geometry and I did further research. Cam goes all the way to the toe end at full lift. There is perhaps some tenths of mm left, practically none. Rocker that I used for the test was new OEM. Febi seems to be very similar.

[digger]

are you able to do a wiping of some colour and show it on the rocker as it can be misleading, i personally think that if there is a little bit of space then probably GTG as the contact area is still a radius not the sharp edge so oil film wont be immediately broken. You could ask dbilas for how far from edge is ok.

This is one of the problems with stock rockers the feet are not long enough so the cam designer profile is limited by velocity else the foot (heel or toe) digs into the cams so you end up needing to use a lower velocity profile which means more duration to get same peak lift numbers. This is why you dont really see 12.5mm lift with 270 degree cams.

Alternatives are

• I believe IE HD may have been changed in last few years as people complained about this issue with even moderate cams. I may have some samples i purchased at various times over last 5 or so years i can dig out.
• Catcams steel rockers have longer pads to address this but uber $$$
• Metric mechanic were developing steel rockers but not sure they have a product for m20 thats available, i think they have m30 ones done though

[digger]

most recent IE HD vs old IE HD rockers

[hasa]

Thanks helping with this issue, digger! I'll try to take even closer photo of the pad when I visit my garage next time.

I currently think that my choise has to be made between these:

1. fall back to Schrick 304. It is proven to work reliably, but perhaps loses some hp compared to dBilas.
2. Take the risk with dBilas cam if I find any rockers that have long enough pads
3. Take the big step and go RHD roller setup. It doubles the cost of the engine but probably is the only viable option. But then I'd be tempted to build new no-compromise bottom end by using S50B30US crank, racetep designed pistons etc... again big $ more. It's difficult to consider where to stop this madness.

I made some measurements of the pad length. It seems that BMW oem rockers have 20mm long pad. Febi might have 20,5mm. But it was difficult to measure reliably. Of course the placement of the pad is important too. And radius of the pad.

[moatilliatta]

I’m not sold on the IE HD rockers as the New Genuine BMW ones have been good. I wonder what the 325is group N cars used or even the 325 group A car.

I know they all didn’t have the hot cam you’re looking for, and understand the profiles issue.

Schrick stiff usually just always work. Don’t they have a 308 Cam?